Production of ferrochromium



UNITED STATES PATENT OFFICE.

JOSEPH E. JOHNSON, Jlh, OF NEW YORK, N. Y.; MARGRAET HILLES JOHNSON EXECU- TRIX OF SAID JOSEPH E J'OHNSON, JR., DECEASED.

' PRODUCTION OF FERROGHROMIUM.

No Drawing. Application filed July 23,

v To all whom it may concern:

Be it known that I, JOSEPH E. JoHNsoN, Jr., a citizen of the United States, residing at New York city, in the county of New York, State of Neiw York, have invented certain new and useful Improvements in Production of \Ferrochromium; and I do hereby declare the following to be a full,

clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

Ferro-chromium, in so far asI am aware,

is now made exclusively in the electric furnace. It was formerly made, to some extent,

in the iron blast furnace, but it was found that the limiting percentage of chromium which could be introduced into'the alloy obtained in the blast furnace was in the neighborhood of This is because, at or about that point, an equilibrium is estab lished, in the furnace, limiting correspondingly the reduotion of the chromium from its compounds and its introduction into the alloy. The most desirable ferro-chromium alloys for commercial use contain 60% and upward of chromium, and these alloys can not be produced at all in the blast furnace by the processes heretofore employed.

My investigations of the iron blast furnace in the alloy to 10% and upward with the effect of keeping down the percentage of carbon in the alloy, which is essential in the production of the highest gradesof ferrochromium. For thedesired result, I do not need a blast consisting wholly of oxygen,

but can use a blast containing from 40 to 50% of oxygen (and a correspondingly lower per cent. of nitrogen) which is muc cheaper to produce than 100% of oxygen.

' By'varying the amount of increase of ogyen and the amount of decrease of nitrogen n the blast, I am enabled to produce ferro- Specification of Letters Patent.

Patented Oct. 5, 1920.

1918. Serial No. 246,346.

chromium containing practically any deslred percentage of chromium and to produce it much more cheaply than can be done in the electric furnace. So also, as above noted, the hearth heat may be so far increased as to reduce a considerable percentage of the silica present and cause the silicon thereof to unite with the ferro-chromium with the result of forcing down the carbon content of the alloy.

Furthermore, if so desired, the alloy, whilefstill in the liquid condition, but in a separate vessel, may be subjected to the ac tion of oxid of iron or oxid of chromium, or both, with the result that these oxids attack the silicon of the alloy, thereby oxidizing it to silica, which, uniting with a portion of the oxid unreduced, passes off as slag, the metal reduced from the oxid thereupon entering the alloy. By this means I can produce an alloy high in chromium and low in both carbon and silicon.

What I claim is:

1. The method of producing in a blast furnace, alloys of iron, high in chromium, which comprises blowing the charge (containing carbon, iron and chrofurnace mium) with a blast richer in oxygen and poorer in nitrogen than the atmosphere, the relative oxygen and nitrogen content of the blast being so proportioned that'an increase in hearth temperatureis obtained sufficient to obtain the desired high chromium content in the alloy; substantially as described 2. The method of producing in a blast furnace, alloys of iron, high in chromium and low in silicon and carbon, which comprises blowing the furnace charge (containing carbon, iron, manganese and silicon) with a blast richer in oxygen and poorer in nitrogen than the atmosphere, the relative oxygen and nitrogen content of the blast being so proportioned that an increase in hearth temperature is produced sufficient to obtainthe desired high chromium content in the alloy and to likewiseincrease the content of silicon at the expense of the carbon content of the alloy; substantially as described.

3. The method of producing in a blast furnace, alloys of iron, high in chromium and low in silicon and "carbon, which comprises blowing the furnace charge (containing carbon, iron, manganese and silicon) with a blast richer in oxygen and, poorer in 

